The present invention relates to an optical detector in which optical filters are disposed between a window material for transmitting light such as an infrared and an ultraviolet ray and detection elements, each optical filter being corresponding to the each detection element. The optical filters are used for selecting and causing only light composed of a predetermined band of wavelengths to be transmitted by means of thin optical films in connection with the detection element.
There is an infrared-ray detector in which four optical filters respectively corresponding to four infrared-ray detection elements have substrates having the same thickness and while the edge faces of the substrates are set in the same plane and bonded together by an adhesive agent. The substrates are disposed in parallel integrally in the form of combined four squares in plan view. Each optical filter is obtained by dicing to scrape the substrate with a thin short-long cut portion and a band pass portion formed on the surface and undersurface. However, it has been impossible to completely prevent an infrared ray (hereinafter called infrared light) composed of other than the predetermined band of wavelengths selected by the short-long cut surface and the band pass surface as well as infrared light (disturbing light) producing an interference effect during measurement from being incident from the edge face (scraped face) of the optical filter thus obtained.
As shown in FIG. 7, for example, out of infrared light passing through an optical filter 70, the infrared light Axe2x80x2 reflected in the optical filter 70 passes through an adhesive agent 77 from the edge face m (scraped face) of the optical filter 70 becomes incident from the edge face (scraped face) of an optical filter 72 adjacent to the optical filter 70. Further, the infrared light Bxe2x80x2 and Cxe2x80x2 reflected from the inner face 73a of the metal case 73 of an infrared-ray detector without passing through four optical filters including the optical filters 70 and 72 becomes incident on the optical filter 70 from the edge face (scraped face) mxe2x80x2 of the optical filter 70, so that infrared light without passing on the short-long cut surface and/or the band pass surface produces such an interference effect.
An object of the present invention made in view of the foregoing circumstances is to provide an optical detector capable of shading disturbing light producing an interference effect.
In order to accomplish the object above, an optical detector according to the invention comprises a window material for transmitting light such as an infrared and an ultraviolet ray therethrough; a sealed case whose opening portion is blocked with said window material; detection elements being formed opposite to said window material in said sealed case; optical filters disposed between said window material and said detection elements, which transmits only light composed of a predetermined band of wavelengths by thin optical films, each optical filter corresponding to each detection elements; and a shielding body supporting said optical filters and preventing any light composed of other than the predetermined band of wavelength selected by said thin optical films and light producing an interference effect during measurement from being transmitted through said optical filters.
Further, in the optical detector, the shielding body includes housing portions for supporting said optical filters.
The invention provides an optical detector in which the surface of the shielding body is positioned higher than the surface of each of the optical filters.
According to the invention, the shielding body has an upper opening through which the light transmitted through the window material passes, a lower opening through which the light composed of the predetermined band of wavelength selected by the optical thin films after the light transmitted through the window material passes through the upper opening, and a filter receiving portion for mounting the optical filters as part of the undersurface of each of the optical filters makes contact with the filter receiving portion in the lower opening.
According to the invention, the shielding body is made of material, which absorbs the light, or the surface of the shielding body is processed by blackening for absorbing the light.